Zombies, also known as Plague Zombies, are victims of a highly contagious and deadly viral infection known as the "Zombie Plague" or the "Curse of Unbelief", spread by the minions of the Chaos GodNurgle. Not only do they die as the result of the disease, they return as undead, mindlessly devoted to adding their former comrades-in-arms to their number by infecting them with the Zombie Plague virus they carry in their saliva and blood. The Curse of Unbelief has appeared in the underhives of Necromunda and in Chaos-influenced regions of the Segmentum Obscurus near the Eye of Terror, with documented instances of undead fighting against the servants of the Emperor going all the way back to the final days of the Great Crusade before the Horus Heresy, such as during the Luna WolvesLegion's assault upon the feral moon of the world of Davin. The first recorded instance of the Zombie Plague in the 41st Millennium was on the world of Hydra Minoris in 757.M41. A quarantine was imposed by the Imperial Navy, trapping 23 billion uninfected people alongside a rising tide of hungry and mindless undead.

The Curse of Unbelief is believed to be a spiritual as much as a physical contagion, hence its name, and the disease is held by the Ecclesiarchy to afflict only those lacking a pure faith in the Emperor. The disease is one of the multitudes of foul contagions spread by the Plague Fleets of Nurgle; most notably the warships of the Chaos ChampionTyphus of the Death GuardTraitor Legion. Plague zombies act very much like the zombies in ancient films; they are mindless, shambling and cannibalistic. The main thing about plague zombies (and zombies in general) is that they are hard to kill and require an accurate shot to the head or complete dismemberment to put them down for good.